What camera profile are you using as your default in ACR 6.3? If you are using the v3 (Camera Standard, Camera Neutral, etc), these require a correction of -0.5 on the exposure slider. I use the v4 profiles which do not require a correction in exposure, but I am not sure these work with ACR 6.3. You should update ACR to the current released version of ACR 6.6 and try the v4 profiles. I get excellent agreement between these and the Nikon Picture Control profiles for my D700.